Epoxidized natural rubber has been conventionally used for rubber products such as tires. Epoxidized natural rubber is prepared, for example, by a production method includes: adding hydrogen peroxide and either formic acid or acetic acid to natural rubber latex stabilized with a surfactant; reacting the resulting performic acid or peracetic acid formed in the latex with the natural rubber for epoxidation; and coagulating, neutralizing, washing, and drying the latex, as needed.
For example, Patent Literature 1 discloses a method for producing epoxidized natural rubber by mixing acetic acid, hydrogen peroxide, and sulfuric acid (a catalyst), allowing the mixture to stand at 40° C. for about 1 to 2 days to prepare peracetic acid, and reacting the obtained peracetic acid with natural rubber latex.
Unfortunately, the above method requires a long time (i.e. 1 to 2 days) to prepare peracetic acid, and thus the epoxidized natural rubber productivity is poor. In addition, the reaction temperature has to be controlled at 40° C., which unfortunately results in high cost for temperature control.